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Date: 4-11-2018
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Date: 5-12-2018
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Date: 6-11-2018
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The name for the metal tungsten is taken from the Swedish, tungsten, for "heavy stone". The symbol has its origins in the discovery of the element in the late 1700's linked to the mineral wolframite. Most German chemists still refer to the element as Wolfram (wolf's metal). Pure tungsten was eventually isolated in 1783 by brothers Juan and Fausto Elhuyar.
Tungsten is known chiefly as the metal in incandescent light bulb filaments (tungsten has the highest melting point of any metal). But a lot of tungsten is also used in the manufacture of tungsten carbide, an extremely hard material used for making cutting tools and abrasives. The metal is also alloyed with steel for very high temperature applications such as rocket engine nozzles.
Very pure tungsten is actually soft enough to be cut with an ordinary hacksaw but generally small amounts of impurities render the metal very hard and brittle. It i very similar to both Mo and Cr. It is straddled by elements having the second and third highest melting points, rhenium, Re, and tantalum, Ta.
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علامات بسيطة في جسدك قد تنذر بمرض "قاتل"
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أول صور ثلاثية الأبعاد للغدة الزعترية البشرية
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وفد كلية الزراعة في جامعة كربلاء يشيد بمشروع الحزام الأخضر
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